1. Field of the Invention
This invention pertains to the general field of optical beam switches and controllers. In particular, the invention provides a simple mechanism for switching any one of a number of parallel beams onto a common optical path.
2. Description of the Prior Art
In optical applications, it is often the case that a beam of particular chromatic or power characteristics is needed among several available choices for use in an optical system. For example, different wavelengths may be preferred for alternative applications, such as multiple laser sources used sequentially in a microarray scanner. Spatially different wavefronts may similarly be desirable, such as beams with varied cross-sectional diameters. In all such cases, some mechanism is provided for selecting the output beam by switching from one input beam to another.
Typically, such switching is accomplished using dichroic beamsplitters. All input beams are reflected into a single optical axis and the dichroic beamsplitters are used to control the wavelength of the output beam, as desired, by energizing a single input beam at a time. This requires the use of multiple dichroic elements, each of which introduces undesirable intensity losses, as well as the sequential energizing and deenergizing of the various light sources, or, in the case of sources that are not efficiently turned on and off, the use of shutters or equivalent mechanisms that add to the cost of the switch. Accordingly, a simpler mechanism for switching between alternative light sources would be a desirable advance in the art.
It is known that a parallel glass plate will translate an incident beam along an axis parallel to the incident optical axis by an amount that depends on the distance between the parallel surfaces in the plate, the index of refraction of the glass, and the angle of incidence of the beam. This property is often used to correct the optical axis position in optical apparatus. As illustrated in FIG. 1, the property can also be used to shift the position of the output beam among parallel alternatives simply by varying the position, and therefore the angle of incidence, of the input beam.
As illustrated in FIG. 2, it is also clear that two reflective surfaces in fixed parallel relation to one another will translate an incident beam along an axis parallel to the incident optical axis by an amount that depends on the distance between the reflective surfaces. Accordingly, this property can similarly be used to shift the position of the output beam among parallel alternatives simply by varying the distance between the surfaces or, equivalently, by rotating the two mirrors while maintaining their relative position (thereby changing the distance traveled between them by the beam after first reflection). The present invention exploits these properties to provide a simple but effective switching mechanism for directing a beam selected from alternative parallel input choices toward a predetermined output optical axis.
The preferred embodiment of the invention consists of the combination of a light source with multiple parallel beams, a pair of opposing mirrors mounted on a rotating fixture, and an aperture defining the optical path of a single output beam. Through the motion of the rotating fixture, the two mirrors shift the location of the output of each input beam reflected by the mirrors so as to selectively channel each beam into the optical path defined by the aperture. Accordingly, the input source corresponding to the output beam may be quickly switched by rotating the fixture/mirror combination to the position that produces the appropriate shift of the beam selected from the light source. Thus, the rotating fixture/mirror combination acts as a switch among the various alternative light sources to produce the desired output beam through the aperture.
According to another embodiment of the invention, the pair of reflective surfaces is replaced by a transparent block similarly mounted on a rotating fixture. Through the motion of the rotating fixture, the transparent block shifts the location of the output of each input beam so as to selectively channel each beam into the optical path defined by the aperture, thereby also acting as an optical switch.
Thus, a benefit derived from the invention is the controllable translation of an optical beam to a position parallel to its propagation axis, which allows the placement of multiple parallel optical beams, one at a time, onto a common optical axis for introduction into an optical system.
Another benefit of the invention is its ability to shift a light beam, whether through reflection or diffraction, without chromatic effects. Because the translation is a function of the rotation angle of the fixture, it can be finely adjusted to compensate for any wavelength-dependent behavior of the device components.
The invention provides the benefit of negligible losses when compared to the serial dichroic beamsplitters used in the prior art. Furthermore, it provides the advantage of a performance that is not substantially limited by the spectral properties of the input beams.
Finally, a further benefit of the invention lies in its general application as a switch in any optical instrument that requires the ability to select one of alternative parallel light beams for use in the single optical path of an optical system.
Various other benefits and advantages of the invention will become clear from its description in the specification that follows and from the novel features particularly pointed out in the appended claims. Therefore, to the accomplishment of the objectives described above, this invention consists of the features hereinafter illustrated in the drawings, fully described in the detailed description of the preferred embodiments and particularly pointed out in the claims. However, such drawings and description disclose only some of the various ways in which the invention may be practiced.